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<div class="section" id="creating-an-llvm-project">
<h1>Creating an LLVM Project<a class="headerlink" href="#creating-an-llvm-project" title="Permalink to this headline">¶</a></h1>
<div class="contents local topic" id="contents">
<ul class="simple">
<li><a class="reference internal" href="#overview" id="id1">Overview</a></li>
<li><a class="reference internal" href="#source-tree-layout" id="id2">Source Tree Layout</a></li>
<li><a class="reference internal" href="#writing-llvm-style-makefiles" id="id3">Writing LLVM Style Makefiles</a><ul>
<li><a class="reference internal" href="#required-variables" id="id4">Required Variables</a></li>
<li><a class="reference internal" href="#variables-for-building-subdirectories" id="id5">Variables for Building Subdirectories</a></li>
<li><a class="reference internal" href="#variables-for-building-libraries" id="id6">Variables for Building Libraries</a></li>
<li><a class="reference internal" href="#variables-for-building-programs" id="id7">Variables for Building Programs</a></li>
<li><a class="reference internal" href="#miscellaneous-variables" id="id8">Miscellaneous Variables</a></li>
</ul>
</li>
<li><a class="reference internal" href="#placement-of-object-code" id="id9">Placement of Object Code</a></li>
<li><a class="reference internal" href="#further-help" id="id10">Further Help</a></li>
</ul>
</div>
<div class="section" id="overview">
<h2><a class="toc-backref" href="#id1">Overview</a><a class="headerlink" href="#overview" title="Permalink to this headline">¶</a></h2>
<p>The LLVM build system is designed to facilitate the building of third party
projects that use LLVM header files, libraries, and tools. In order to use
these facilities, a <code class="docutils literal notranslate"><span class="pre">Makefile</span></code> from a project must do the following things:</p>
<ul class="simple">
<li>Set <code class="docutils literal notranslate"><span class="pre">make</span></code> variables. There are several variables that a <code class="docutils literal notranslate"><span class="pre">Makefile</span></code> needs
to set to use the LLVM build system:<ul>
<li><code class="docutils literal notranslate"><span class="pre">PROJECT_NAME</span></code> - The name by which your project is known.</li>
<li><code class="docutils literal notranslate"><span class="pre">LLVM_SRC_ROOT</span></code> - The root of the LLVM source tree.</li>
<li><code class="docutils literal notranslate"><span class="pre">LLVM_OBJ_ROOT</span></code> - The root of the LLVM object tree.</li>
<li><code class="docutils literal notranslate"><span class="pre">PROJ_SRC_ROOT</span></code> - The root of the project’s source tree.</li>
<li><code class="docutils literal notranslate"><span class="pre">PROJ_OBJ_ROOT</span></code> - The root of the project’s object tree.</li>
<li><code class="docutils literal notranslate"><span class="pre">PROJ_INSTALL_ROOT</span></code> - The root installation directory.</li>
<li><code class="docutils literal notranslate"><span class="pre">LEVEL</span></code> - The relative path from the current directory to the
project’s root <code class="docutils literal notranslate"><span class="pre">($PROJ_OBJ_ROOT)</span></code>.</li>
</ul>
</li>
<li>Include <code class="docutils literal notranslate"><span class="pre">Makefile.config</span></code> from <code class="docutils literal notranslate"><span class="pre">$(LLVM_OBJ_ROOT)</span></code>.</li>
<li>Include <code class="docutils literal notranslate"><span class="pre">Makefile.rules</span></code> from <code class="docutils literal notranslate"><span class="pre">$(LLVM_SRC_ROOT)</span></code>.</li>
</ul>
<p>There are two ways that you can set all of these variables:</p>
<ul class="simple">
<li>You can write your own <code class="docutils literal notranslate"><span class="pre">Makefiles</span></code> which hard-code these values.</li>
<li>You can use the pre-made LLVM sample project. This sample project includes
<code class="docutils literal notranslate"><span class="pre">Makefiles</span></code>, a configure script that can be used to configure the location
of LLVM, and the ability to support multiple object directories from a single
source directory.</li>
</ul>
<p>If you want to devise your own build system, studying other projects and LLVM
<code class="docutils literal notranslate"><span class="pre">Makefiles</span></code> will probably provide enough information on how to write your own
<code class="docutils literal notranslate"><span class="pre">Makefiles</span></code>.</p>
</div>
<div class="section" id="source-tree-layout">
<h2><a class="toc-backref" href="#id2">Source Tree Layout</a><a class="headerlink" href="#source-tree-layout" title="Permalink to this headline">¶</a></h2>
<p>In order to use the LLVM build system, you will want to organize your source
code so that it can benefit from the build system’s features. Mainly, you want
your source tree layout to look similar to the LLVM source tree layout.</p>
<p>Underneath your top level directory, you should have the following directories:</p>
<p><strong>lib</strong></p>
<blockquote>
<div><p>This subdirectory should contain all of your library source code. For each
library that you build, you will have one directory in <strong>lib</strong> that will
contain that library’s source code.</p>
<p>Libraries can be object files, archives, or dynamic libraries. The <strong>lib</strong>
directory is just a convenient place for libraries as it places them all in
a directory from which they can be linked later.</p>
</div></blockquote>
<p><strong>include</strong></p>
<blockquote>
<div><p>This subdirectory should contain any header files that are global to your
project. By global, we mean that they are used by more than one library or
executable of your project.</p>
<p>By placing your header files in <strong>include</strong>, they will be found
automatically by the LLVM build system. For example, if you have a file
<strong>include/jazz/note.h</strong>, then your source files can include it simply with
<strong>#include “jazz/note.h”</strong>.</p>
</div></blockquote>
<p><strong>tools</strong></p>
<blockquote>
<div>This subdirectory should contain all of your source code for executables.
For each program that you build, you will have one directory in <strong>tools</strong>
that will contain that program’s source code.</div></blockquote>
<p><strong>test</strong></p>
<blockquote>
<div><p>This subdirectory should contain tests that verify that your code works
correctly. Automated tests are especially useful.</p>
<p>Currently, the LLVM build system provides basic support for tests. The LLVM
system provides the following:</p>
</div></blockquote>
<ul>
<li><p class="first">LLVM contains regression tests in <code class="docutils literal notranslate"><span class="pre">llvm/test</span></code>. These tests are run by the
<a class="reference internal" href="CommandGuide/lit.html"><span class="doc">Lit</span></a> testing tool. This test procedure uses <code class="docutils literal notranslate"><span class="pre">RUN</span></code>
lines in the actual test case to determine how to run the test. See the
<a class="reference internal" href="TestingGuide.html"><span class="doc">LLVM Testing Infrastructure Guide</span></a> for more details.</p>
</li>
<li><p class="first">LLVM contains an optional package called <code class="docutils literal notranslate"><span class="pre">llvm-test</span></code>, which provides
benchmarks and programs that are known to compile with the Clang front
end. You can use these programs to test your code, gather statistical
information, and compare it to the current LLVM performance statistics.</p>
<p>Currently, there is no way to hook your tests directly into the <code class="docutils literal notranslate"><span class="pre">llvm/test</span></code>
testing harness. You will simply need to find a way to use the source
provided within that directory on your own.</p>
</li>
</ul>
<p>Typically, you will want to build your <strong>lib</strong> directory first followed by your
<strong>tools</strong> directory.</p>
</div>
<div class="section" id="writing-llvm-style-makefiles">
<h2><a class="toc-backref" href="#id3">Writing LLVM Style Makefiles</a><a class="headerlink" href="#writing-llvm-style-makefiles" title="Permalink to this headline">¶</a></h2>
<p>The LLVM build system provides a convenient way to build libraries and
executables. Most of your project Makefiles will only need to define a few
variables. Below is a list of the variables one can set and what they can
do:</p>
<div class="section" id="required-variables">
<h3><a class="toc-backref" href="#id4">Required Variables</a><a class="headerlink" href="#required-variables" title="Permalink to this headline">¶</a></h3>
<p><code class="docutils literal notranslate"><span class="pre">LEVEL</span></code></p>
<blockquote>
<div>This variable is the relative path from this <code class="docutils literal notranslate"><span class="pre">Makefile</span></code> to the top
directory of your project’s source code. For example, if your source code
is in <code class="docutils literal notranslate"><span class="pre">/tmp/src</span></code>, then the <code class="docutils literal notranslate"><span class="pre">Makefile</span></code> in <code class="docutils literal notranslate"><span class="pre">/tmp/src/jump/high</span></code>
would set <code class="docutils literal notranslate"><span class="pre">LEVEL</span></code> to <code class="docutils literal notranslate"><span class="pre">"../.."</span></code>.</div></blockquote>
</div>
<div class="section" id="variables-for-building-subdirectories">
<h3><a class="toc-backref" href="#id5">Variables for Building Subdirectories</a><a class="headerlink" href="#variables-for-building-subdirectories" title="Permalink to this headline">¶</a></h3>
<p><code class="docutils literal notranslate"><span class="pre">DIRS</span></code></p>
<blockquote>
<div>This is a space separated list of subdirectories that should be built. They
will be built, one at a time, in the order specified.</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">PARALLEL_DIRS</span></code></p>
<blockquote>
<div>This is a list of directories that can be built in parallel. These will be
built after the directories in DIRS have been built.</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">OPTIONAL_DIRS</span></code></p>
<blockquote>
<div>This is a list of directories that can be built if they exist, but will not
cause an error if they do not exist. They are built serially in the order
in which they are listed.</div></blockquote>
</div>
<div class="section" id="variables-for-building-libraries">
<h3><a class="toc-backref" href="#id6">Variables for Building Libraries</a><a class="headerlink" href="#variables-for-building-libraries" title="Permalink to this headline">¶</a></h3>
<p><code class="docutils literal notranslate"><span class="pre">LIBRARYNAME</span></code></p>
<blockquote>
<div>This variable contains the base name of the library that will be built. For
example, to build a library named <code class="docutils literal notranslate"><span class="pre">libsample.a</span></code>, <code class="docutils literal notranslate"><span class="pre">LIBRARYNAME</span></code> should
be set to <code class="docutils literal notranslate"><span class="pre">sample</span></code>.</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">BUILD_ARCHIVE</span></code></p>
<blockquote>
<div>By default, a library is a <code class="docutils literal notranslate"><span class="pre">.o</span></code> file that is linked directly into a
program. To build an archive (also known as a static library), set the
<code class="docutils literal notranslate"><span class="pre">BUILD_ARCHIVE</span></code> variable.</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">SHARED_LIBRARY</span></code></p>
<blockquote>
<div>If <code class="docutils literal notranslate"><span class="pre">SHARED_LIBRARY</span></code> is defined in your Makefile, a shared (or dynamic)
library will be built.</div></blockquote>
</div>
<div class="section" id="variables-for-building-programs">
<h3><a class="toc-backref" href="#id7">Variables for Building Programs</a><a class="headerlink" href="#variables-for-building-programs" title="Permalink to this headline">¶</a></h3>
<p><code class="docutils literal notranslate"><span class="pre">TOOLNAME</span></code></p>
<blockquote>
<div>This variable contains the name of the program that will be built. For
example, to build an executable named <code class="docutils literal notranslate"><span class="pre">sample</span></code>, <code class="docutils literal notranslate"><span class="pre">TOOLNAME</span></code> should be set
to <code class="docutils literal notranslate"><span class="pre">sample</span></code>.</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">USEDLIBS</span></code></p>
<blockquote>
<div><p>This variable holds a space separated list of libraries that should be
linked into the program. These libraries must be libraries that come from
your <strong>lib</strong> directory. The libraries must be specified without their
<code class="docutils literal notranslate"><span class="pre">lib</span></code> prefix. For example, to link <code class="docutils literal notranslate"><span class="pre">libsample.a</span></code>, you would set
<code class="docutils literal notranslate"><span class="pre">USEDLIBS</span></code> to <code class="docutils literal notranslate"><span class="pre">sample.a</span></code>.</p>
<p>Note that this works only for statically linked libraries.</p>
</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">LLVMLIBS</span></code></p>
<blockquote>
<div><p>This variable holds a space separated list of libraries that should be
linked into the program. These libraries must be LLVM libraries. The
libraries must be specified without their <code class="docutils literal notranslate"><span class="pre">lib</span></code> prefix. For example, to
link with a driver that performs an IR transformation you might set
<code class="docutils literal notranslate"><span class="pre">LLVMLIBS</span></code> to this minimal set of libraries <code class="docutils literal notranslate"><span class="pre">LLVMSupport.a</span> <span class="pre">LLVMCore.a</span>
<span class="pre">LLVMBitReader.a</span> <span class="pre">LLVMAsmParser.a</span> <span class="pre">LLVMAnalysis.a</span> <span class="pre">LLVMTransformUtils.a</span>
<span class="pre">LLVMScalarOpts.a</span> <span class="pre">LLVMTarget.a</span></code>.</p>
<p>Note that this works only for statically linked libraries. LLVM is split
into a large number of static libraries, and the list of libraries you
require may be much longer than the list above. To see a full list of
libraries use: <code class="docutils literal notranslate"><span class="pre">llvm-config</span> <span class="pre">--libs</span> <span class="pre">all</span></code>. Using <code class="docutils literal notranslate"><span class="pre">LINK_COMPONENTS</span></code> as
described below, obviates the need to set <code class="docutils literal notranslate"><span class="pre">LLVMLIBS</span></code>.</p>
</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">LINK_COMPONENTS</span></code></p>
<blockquote>
<div>This variable holds a space separated list of components that the LLVM
<code class="docutils literal notranslate"><span class="pre">Makefiles</span></code> pass to the <code class="docutils literal notranslate"><span class="pre">llvm-config</span></code> tool to generate a link line for
the program. For example, to link with all LLVM libraries use
<code class="docutils literal notranslate"><span class="pre">LINK_COMPONENTS</span> <span class="pre">=</span> <span class="pre">all</span></code>.</div></blockquote>
<p><code class="docutils literal notranslate"><span class="pre">LIBS</span></code></p>
<blockquote>
<div><p>To link dynamic libraries, add <code class="docutils literal notranslate"><span class="pre">-l<library</span> <span class="pre">base</span> <span class="pre">name></span></code> to the <code class="docutils literal notranslate"><span class="pre">LIBS</span></code>
variable. The LLVM build system will look in the same places for dynamic
libraries as it does for static libraries.</p>
<p>For example, to link <code class="docutils literal notranslate"><span class="pre">libsample.so</span></code>, you would have the following line in
your <code class="docutils literal notranslate"><span class="pre">Makefile</span></code>:</p>
<blockquote>
<div><div class="highlight-makefile notranslate"><div class="highlight"><pre><span></span><span class="nv">LIBS</span> <span class="o">+=</span> -lsample
</pre></div>
</div>
</div></blockquote>
</div></blockquote>
<p>Note that <code class="docutils literal notranslate"><span class="pre">LIBS</span></code> must occur in the Makefile after the inclusion of
<code class="docutils literal notranslate"><span class="pre">Makefile.common</span></code>.</p>
</div>
<div class="section" id="miscellaneous-variables">
<h3><a class="toc-backref" href="#id8">Miscellaneous Variables</a><a class="headerlink" href="#miscellaneous-variables" title="Permalink to this headline">¶</a></h3>
<p><code class="docutils literal notranslate"><span class="pre">CFLAGS</span></code> & <code class="docutils literal notranslate"><span class="pre">CPPFLAGS</span></code></p>
<blockquote>
<div><p>This variable can be used to add options to the C and C++ compiler,
respectively. It is typically used to add options that tell the compiler
the location of additional directories to search for header files.</p>
<p>It is highly suggested that you append to <code class="docutils literal notranslate"><span class="pre">CFLAGS</span></code> and <code class="docutils literal notranslate"><span class="pre">CPPFLAGS</span></code> as
opposed to overwriting them. The master <code class="docutils literal notranslate"><span class="pre">Makefiles</span></code> may already have
useful options in them that you may not want to overwrite.</p>
</div></blockquote>
</div>
</div>
<div class="section" id="placement-of-object-code">
<h2><a class="toc-backref" href="#id9">Placement of Object Code</a><a class="headerlink" href="#placement-of-object-code" title="Permalink to this headline">¶</a></h2>
<p>The final location of built libraries and executables will depend upon whether
you do a <code class="docutils literal notranslate"><span class="pre">Debug</span></code>, <code class="docutils literal notranslate"><span class="pre">Release</span></code>, or <code class="docutils literal notranslate"><span class="pre">Profile</span></code> build.</p>
<p>Libraries</p>
<blockquote>
<div>All libraries (static and dynamic) will be stored in
<code class="docutils literal notranslate"><span class="pre">PROJ_OBJ_ROOT/<type>/lib</span></code>, where <em>type</em> is <code class="docutils literal notranslate"><span class="pre">Debug</span></code>, <code class="docutils literal notranslate"><span class="pre">Release</span></code>, or
<code class="docutils literal notranslate"><span class="pre">Profile</span></code> for a debug, optimized, or profiled build, respectively.</div></blockquote>
<p>Executables</p>
<blockquote>
<div>All executables will be stored in <code class="docutils literal notranslate"><span class="pre">PROJ_OBJ_ROOT/<type>/bin</span></code>, where <em>type</em>
is <code class="docutils literal notranslate"><span class="pre">Debug</span></code>, <code class="docutils literal notranslate"><span class="pre">Release</span></code>, or <code class="docutils literal notranslate"><span class="pre">Profile</span></code> for a debug, optimized, or
profiled build, respectively.</div></blockquote>
</div>
<div class="section" id="further-help">
<h2><a class="toc-backref" href="#id10">Further Help</a><a class="headerlink" href="#further-help" title="Permalink to this headline">¶</a></h2>
<p>If you have any questions or need any help creating an LLVM project, the LLVM
team would be more than happy to help. You can always post your questions to
the <a class="reference external" href="http://lists.llvm.org/pipermail/llvm-dev/">LLVM Developers Mailing List</a>.</p>
</div>
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